| Message ID | 20250122062332.577009-1-irogers@google.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Support dynamic opening of capstone/llvm remove BUILD_NONDISTRO | expand |
On Tue, Jan 21, 2025 at 10:23:15PM -0800, Ian Rogers wrote: > Linking against libcapstone and libLLVM can be a significant increase > in dependencies and size of memory footprint. For something like `perf > record` the disassembler and addr2line functionality won't be > used. Support dynamically loading these libraries using dlopen and > then calling the appropriate functions found using dlsym. It's unclear to me what this actually fixes. If the code is not used it should not be faulted in and the dynamic linker is lazy too, so if it's not used, it won't even be linked. I don't see any numbers, but it won't surprise me if it improved actual run time or memory usage significantly. -Andi
On Wed, Jan 22, 2025 at 7:21 AM Andi Kleen <ak@linux.intel.com> wrote: > > On Tue, Jan 21, 2025 at 10:23:15PM -0800, Ian Rogers wrote: > > Linking against libcapstone and libLLVM can be a significant increase > > in dependencies and size of memory footprint. For something like `perf > > record` the disassembler and addr2line functionality won't be > > used. Support dynamically loading these libraries using dlopen and > > then calling the appropriate functions found using dlsym. > > It's unclear to me what this actually fixes. If the code is not used > it should not be faulted in and the dynamic linker is lazy too, so > if it's not used, it won't even be linked. > > I don't see any numbers, but it won't surprise me if it improved > actual run time or memory usage significantly. In certain scenarios, like data centers, it can be useful to statically link all your dependencies to avoid dll hell. The X86 disassembler alone in libllvm is of a size comparable to the perf tool - I think this speaks to us doing a reasonably good job of size optimization of the events/metrics in the perf tool. We want these dependencies for the performance over forking objdump and addr2line, but we don't want it baked in - unless the person doing the build wants this and this is still the default if the libraries are detected by Makefile.config. Using dlopen also means distributions can have a perf tool that doesn't drag in libLLVM.so and a universe of dependencies, but when it is installed get the performance advantages. In data centres having fast disassembly/addr2line is less of a priority over the binary size cost replicated over 10,000s of machines because those machines don't tend to be running the annotate/report commands. Fwiw, Namhyung's uftrace is doing something similar for python: https://github.com/namhyung/uftrace/blob/master/utils/script-python.c#L139 and I wish the perf tool were also doing this. I think it is much nicer to have the tool fail at runtime because of a missing dependency which you can then install should you want it, rather than doing an equivalent within the code base with #ifdefs and needing users to recompile. This patch series significantly reduces the #ifdefs in places like the core disasm code. Thanks, Ian
Linking against libcapstone and libLLVM can be a significant increase in dependencies and size of memory footprint. For something like `perf record` the disassembler and addr2line functionality won't be used. Support dynamically loading these libraries using dlopen and then calling the appropriate functions found using dlsym. BUILD_NONDISTRO is used to build perf against the license incompatible libbfd and libiberty libraries. As this has been opt-in for nearly 2 years, commit dd317df07207 ("perf build: Make binutil libraries opt in"), remove the code to simplify the code base. The patch series: 1) does some initial clean up; 2) moves the capstone and LLVM code to their own C files, 3) simplifies a little the capstone code; 4) adds perf_ variants of the functions that will either directly call the function or use dlsym to discover it; 5) adds BPF JIT disassembly support to LLVM and capstone disassembly; 6) removes the BUILD_NONDISTRO code, reduces scope and removes what's possible. The addr2line LLVM functionality is written in C++. To avoid linking against libLLVM for this, a new LIBLLVM_DYNAMIC option is added where the C++ code with the libLLVM dependency will be built into a libperf-llvm.so and that dlsym-ed and called against. Ideally LLVM would extend their C API to avoid this. The libbfd BPF disassembly supported source lines, this wasn't ported to the capstone and LLVM disassembly. v2: Add mangling of the function names in libperf-llvm.so to avoid potential infinite recursion. Add BPF JIT disassembly support to LLVM and capstone. Add/rebase the BUILD_NONDISTRO cleanup onto the series from: https://lore.kernel.org/lkml/20250111202851.1075338-1-irogers@google.com/ Some other minor additional clean up. Ian Rogers (17): perf build: Remove libtracefs configuration perf map: Constify objdump offset/address conversion APIs perf capstone: Move capstone functionality into its own file perf llvm: Move llvm functionality into its own file perf capstone: Remove open_capstone_handle perf capstone: Support for dlopen-ing libcapstone.so perf llvm: Support for dlopen-ing libLLVM.so perf llvm: Mangle libperf-llvm.so function names perf dso: Move read_symbol from llvm/capstone to dso perf dso: Support BPF programs in dso__read_symbol perf llvm: Disassemble cleanup perf dso: Clean up read_symbol error handling perf build: Remove libbfd support perf build: Remove libiberty support perf build: Remove unused defines perf disasm: Remove disasm_bpf perf disasm: Make ins__scnprintf and ins__is_nop static tools/perf/Documentation/perf-check.txt | 1 - tools/perf/Makefile.config | 90 +--- tools/perf/Makefile.perf | 35 +- tools/perf/builtin-check.c | 1 - tools/perf/builtin-script.c | 2 - tools/perf/tests/Build | 1 - tools/perf/tests/builtin-test.c | 1 - tools/perf/tests/make | 4 +- tools/perf/tests/pe-file-parsing.c | 101 ---- tools/perf/tests/tests.h | 1 - tools/perf/util/Build | 5 +- tools/perf/util/annotate.h | 1 - tools/perf/util/capstone.c | 682 ++++++++++++++++++++++++ tools/perf/util/capstone.h | 24 + tools/perf/util/demangle-cxx.cpp | 22 +- tools/perf/util/disasm.c | 632 +--------------------- tools/perf/util/disasm.h | 5 +- tools/perf/util/disasm_bpf.c | 195 ------- tools/perf/util/disasm_bpf.h | 12 - tools/perf/util/dso.c | 98 ++++ tools/perf/util/dso.h | 4 + tools/perf/util/llvm-c-helpers.cpp | 120 ++++- tools/perf/util/llvm-c-helpers.h | 24 +- tools/perf/util/llvm.c | 489 +++++++++++++++++ tools/perf/util/llvm.h | 24 + tools/perf/util/map.c | 19 +- tools/perf/util/map.h | 6 +- tools/perf/util/print_insn.c | 117 +--- tools/perf/util/srcline.c | 306 +---------- tools/perf/util/srcline.h | 6 + tools/perf/util/symbol-elf.c | 95 ---- tools/perf/util/symbol.c | 135 ----- tools/perf/util/symbol.h | 4 - 33 files changed, 1552 insertions(+), 1710 deletions(-) delete mode 100644 tools/perf/tests/pe-file-parsing.c create mode 100644 tools/perf/util/capstone.c create mode 100644 tools/perf/util/capstone.h delete mode 100644 tools/perf/util/disasm_bpf.c delete mode 100644 tools/perf/util/disasm_bpf.h create mode 100644 tools/perf/util/llvm.c create mode 100644 tools/perf/util/llvm.h